The present invention relates to an apparatus for opening and closing a bin lid from below. Bins utilized on farms and in industry for storing grain or other aggregate materials are most often much taller than a man. Consequently, in the past a man was required to climb a ladder to the top of the bin in order to reach and open or close a top bin lid. The opening in the top of the bin which is closed by the bin lid is usually utilized for loading material into the bin and/or gaining access to the interior of the bin.
Requiring a man to climb to the top of a bin in order to open or close a bin lid is both inefficient and somewhat dangerous. It has been recognized in the art that a ground controlled bin lid opening and closing apparatus would eliminate the above-mentioned inefficiency and danger. One prior art scheme provided a series of rigid mechanical linkages pivotally assembled and extending from the bin lid to within reach of a man on the ground. One problem encountered with this prior art design is that the bin lid when opened was pivoted only 90.degree. and thus would stick straight up in the air. This position may cause problems when equipment such as a feed truck with an auger or other portable conveying equipment is attempted to be positioned over the top loading opening and collisions between the loading equipment and the bin lid were not uncommon, sometimes causing damage to the bin lid, the bin lid linkage, or the loading equipment.
In another assembly produced by the assignee herein, a bin lid which is pivotally mounted about a first pivot axis over the top opening is spring-biased to the closed position by a first spring. A lever arm mounted to the top of the bin lid on a second pivot axis is also spring-biased by a second spring to a position extending upwardly with respect to the lid. A chain extending from the ground, is threaded over a pulley on a lever arm to the side of the lid opposite the pivot axis. When pulled, the chain caused the lever arm to move downwardly and the lid to pivot about the first axis towards an open position against the bias of the first spring. Once the lever arm reached its downward limit of travel, continued pulling of the chain would cause the lid to start pivoting about the second pivot axis such that the bin lid would move toward the lever arm against the bias of the second spring. In this manner the bin lid was able to pivot approximately 180.degree. from the closed position and be completely removed from above the plane of the bin opening, greatly lessening the chances of collision between the lid assembly and bin loading equipment. When the chain was released, the spring bias of the first spring would return the lid to the closed position and the spring bias of the second spring would return the lever arm to its original position.
One drawback of this apparatus is that it is relatively expensive, requiring an undue number of pivot brackets, springs, etc. Another drawback is that the optimal spring for biasing the lid closed and conveniently allowing a man to pull against the spring bias is not sufficiently strong to hold the lid closed during high wind conditions. Another problem encountered is that during assembly of the lid on the bin loading opening coaming, the assembler must bolt the lid to the coaming while various parts of the lid were under a strong spring bias in a direction away from the position in which it is to be secured.